1. Field of the Invention
The present invention relates to a method for producing a group III nitride semiconductor light emitting element having a reflective film including Ag or an Ag alloy provided in an insulating film.
2. Background Art
A group III nitride semiconductor light emitting element provided with a reflective film including Ag provided in an insulating film, or a flip-chip type group III nitride semiconductor light emitting element provided with a reflective electrode including Ag as a p-electrode is conventionally known. For example, Patent Document 1 discloses a group III nitride semiconductor light emitting element having a structure that a p-electrode and an n-electrode are provided on the same surface side, an area of from the p-electrode to the n-electrode is covered with an insulating film, and a reflective film is provided in the insulating film. Patent Document 2 discloses a group III nitride semiconductor light emitting element including a p-type layer, a reflective electrode formed on the p-type layer, and an insulating layer formed on the reflective electrode. Formation of those reflective film and reflective electrode requires patterning to a given area.
Patent Document 1: JP-A-2005-302747
Patent Document 2: JP-A-2003-168823
However, in a case that a lift-off method is used in the patterning of a reflective film and a reflective electrode, a resist film formed has an inversed taper shape. As a result, the reflective film or the reflective electrode on an area becoming a shadow of the resist film has a taper shape, and has a small thickness. Thus, uniform thickness cannot be achieved. This particularly becomes a problem when a reflective film or a reflective electrode includes a multilayer. In a method for patterning by wet etching, where a liquid remover having strong detergency is used in resist removal after patterning, a reflective film is etched. In resist removal by ashing. Ag flocculates by oxidation and reflectivity is decreased. For those reasons, a liquid remover having weak detergency must be used for resist removal. However, residue of the resist is increased, and this gives rise to the problem in adhesion to an insulating film formed on a reflective film.